The long-term objectives of this research are to evaluate the role of phonation in enhancing oral communication in patients with motor speech disorders and to document fundamental mechanisms associated with treatment- related change. The following specific aims are to be accomplished in a five year period: 1) define the mechanism of glottal incompetence in patients with idiopathic Parkinson's disease and determine the relationship between patterns of laryngeal electromyographic (cricothyroid (CT), thyroarytenoid (TA) & lateral cricoarytenoid (LCA)) activity, subglottal air pressure and sound pressure level in these patients; 2) evaluate the changes in patterns of laryngeal EMG (CT, TA & LCA) activity, glottal competence, subglottal air pressure and sound pressure level after intensive voice treatment; 3) evaluate the impact of intensive voice treatment on mandibular (medial pterygoid (MP) & anterior belly of digastric (ABD)) and labial (orbicularis oris superior & inferior (OOS & OO1)) muscle activity, labial kinematics and articulatory acoustics; 4) establish the interactive roles of phonatory and articulatory enhancement on phonetic accuracy and speech intelligibility; 5) evaluate the impact of intensive voice treatment on other motor speech disorders characterized by glottal incompetence. The following variables will be measured: sound pressure level, subglottal air pressure, electromyographic activity from laryngeal (CT, TA & LCA), labial (001 & ))S) and mandibular (MP & ABD) muscles, labial kinematics, vocal fold adduction, phonetic accuracy, acoustic characteristics of speech and speech intelligibility. Data will be collected from patients with glottal incompetence (hypophonia) accompanying idiopathic Parkinson's disease, multiple sclerosis, closed head injury and cerebral vascular accidents. This programmatic research will address these aims through documentation of system-wide effects of phonatory effort treatment. This multi-level assessment of enhanced oral communication will generate data of relevance to models of treatment efficacy and theories of motor speech production.